The previous build_with_updated_interfaces_of_linux_v4.8_and_above.patch
does not alloc struct ahash_request before using it. This will cause the
kernel call trace below when calling gen_scsiid on kernel 4.8 or later
version.

This patch normalizes the calling of ahash API according to the example
in kernel doc Documentation/crypto/api-intro.txt.

BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
IP: [<ffffffffa0008d45>] volume_add+0x625/0x7f0 [iscsi_trgt]
PGD dd77067 PUD dd7c067 PMD 0 
Oops: 0000 [#1] PREEMPT SMP
Modules linked in: iscsi_trgt(O)
CPU: 0 PID: 350 Comm: ietd Tainted: G           O    4.8.12-yocto-standard #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014
task: ffff88000dfe2c00 task.stack: ffff88000de88000
RIP: 0010:[<ffffffffa0008d45>]  [<ffffffffa0008d45>] volume_add+0x625/0x7f0 [iscsi_trgt]
RSP: 0018:ffff88000de8bd90  EFLAGS: 00000206
RAX: 000000000000ddfa RBX: ffff88000ddd1d78 RCX: ffffea0000000000
RDX: 0000000000000600 RSI: 0000000000000000 RDI: ffff88000ddd1c14
RBP: ffff88000de8be38 R08: ffff88000de44180 R09: ffff88000de8bdd0
R10: 000000000000002c R11: 0000000000000000 R12: ffff88000ddfa600
R13: 0000000000000000 R14: 0000000000000000 R15: ffff88000de92200
FS:  00007f767548b700(0000) GS:ffff88000fc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000020 CR3: 000000000dd2d000 CR4: 00000000000006f0
Stack:
 ffff88000de8bdd0 ffff88000dc1b3d0 ffff88000ddfa650 ffff88000ddfa660
 ffff88000df8f000 ffff88000ddd1c00 ffff88000de44180 0000000000000000
 ffffea0000377440 0000000f00000c14 0000000000000000 0000000000000000
Call Trace:
 [<ffffffffa0006547>] ioctl+0x217/0x390 [iscsi_trgt]
 [<ffffffff81192574>] do_vfs_ioctl+0x94/0x5c0
 [<ffffffff8117ff73>] ? vfs_read+0xf3/0x120
 [<ffffffff81192b19>] SyS_ioctl+0x79/0x90
 [<ffffffff8191a45b>] entry_SYSCALL_64_fastpath+0x13/0x8f
Code: 4c 01 e0 0f 82 a2 01 00 00 48 b9 00 00 00 80 ff 77 00 00 48 01
c8 45 31 f6 48 b9 00 00 00 00 00 ea ff ff 89 54 24 68 48 c1 e8 0c <49>
8b 56 20 4c 89 44 24 20 4c 89 f7 48 c1 e0 06 c7 44 24 6c 04 
RIP  [<ffffffffa0008d45>] volume_add+0x625/0x7f0 [iscsi_trgt]
 RSP <ffff88000de8bd90>
CR2: 0000000000000020
end trace cd2016297df21635 ]
ietd_response_recv 200 0 -5
Input/output error.

Upstream-Status: Pending [This patch is based on the previous one which
has not been merged upstream.]

Signed-off-by: Zhe He <zhe.he@windriver.com>

--- iscsitarget-1.4.20.3+svn502_orig/kernel/volume.c	2017-01-18 08:57:56.752187402 +0800
+++ iscsitarget-1.4.20.3+svn502/kernel/volume.c	2017-01-18 09:02:44.164195234 +0800
@@ -93,13 +93,14 @@ static void gen_scsiid(struct iet_volume
 
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 8, 0)
 	tfm = crypto_alloc_ahash("md5", 0, CRYPTO_ALG_ASYNC);
+	hash = ahash_request_alloc(tfm, GFP_ATOMIC);
 #else
 	hash.tfm = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC);
 	hash.flags = 0;
 #endif
 
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 8, 0)
-	if (!IS_ERR(tfm)) {
+	if (tfm && !IS_ERR(tfm)) {
 #else
 	if (!IS_ERR(hash.tfm)) {
 #endif
@@ -116,10 +117,13 @@ static void gen_scsiid(struct iet_volume
 		nbytes += sizeof(volume->lun);
 
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 8, 0)
-		crypto_ahash_init(hash);
+		ahash_request_set_callback(hash, 0, NULL, NULL);
 		ahash_request_set_crypt(hash, sg, volume->scsi_id, nbytes);
-		crypto_ahash_update(hash);
 		crypto_ahash_digest(hash);
+		crypto_ahash_init(hash);
+		crypto_ahash_update(hash);
+		crypto_ahash_final(hash);
+		ahash_request_free(hash);
 		crypto_free_ahash(tfm);
 #else
 		crypto_hash_init(&hash);